Stabilization of peroxy carboxylic acids



oxidizers and have pounds.

United States Patent Ofiice 3,130,169 STABILIZATION F PEROXY CARBOXYLIC ACIDS John H. Blumbergs, Highland Park, and Harold K.

Latourette, Pennington, N.J., assignors to FMC Corporation, a corporation of Delaware No Drawing. Filed June 26, 1961, Ser. No. 119,325

9 Claims. (Cl. 252186) The present invention relates to a process for stabilizing organic solutions of peroxycarboxylic acids.

It is known that peroxycarboxylic acids are excellent great utility in epoxidizing olefinic com- These acids are especially valuable for the epoxidation of non-volatile, water-insoluble, unsaturated {compounds which cannot be converted to oxirane com- ,pounds by direct oxidation with oxygen. A description .1 of their use in epoxidation reactions is given in Swerns article from Chemical Reviews, 1949, at pages 1-68.

Organic solutions of peroxycarboxylic acids are desirable for supplying oxygen in various organic oxidations, e.g., epoxidation reactions, because various peroxycarboxylic acids have higher oxidation potentials, and are more selective than the lower aliphatic peroxycarboxylic acids, such as peroxyacetic acid. Despite this, the only peroxycarboxylic acid which is extensively used in commercial practice is peroxyacetic acid. Other peroxycarboxylic acids have not been used, despite their obvious advantages, because they could not be supplied in stable organic solutions. The rapid decomposition rate of organic solutions of these peroxycarboxylic acids precludes maintaining any supply of organic peroxycarboxylic acid solutions not intended for immediate use. The decomposition takes place according to the following equation:

volume 45, August Organic solutions of peroxycarboxylic acids are desirable since almost all of the peroxycarboxylic acids are relatively water insoluble except for a few lower aliphatic peroxycarboxylic acids such as peroxyformic acid and peroxyacetic acid. The higher aliphatic peroxycarboxylic acids are relatively water insoluble. As a result of the instability of organic solutions of peroxycarboxylic acids, these solutions are made up just prior to being used in chemical reactions such as epoxidations.

The extent of this decomposition can be readily appreciated when it is found that a 21% solution of peroxybenzoic acid in benzene which was stored at room temperature for 34 days, showed a loss of over 91% of its active oxygen. Decomposition at this rate cannot be tolerated where immediate use of the chemical is not contemplated. As a result of this serious, continuous decomposition, there has been an urgent need for some means of preparing organic solutions of peroxycarboxylic acids whose storage stability is within acceptable limits, without material loss of their active-oxygen content.

It is an object of the present invention to prepare compositions of peroxycarboxylic acids in organic solvents which are stable against loss of active oxygen.

It is a further object of the present invention to teach Patented Apr. 21, 1964 a process for producing compositions of peroxycarboxylic acids in organic solvent mixtures which are stable against loss of active oxygen.

It has now been found, unexpectedly, that peroxycarboxylic acids which do not contain oxidizable groups can be stabilized against decomposition by employing a saturated aliphatic tertiary alcohol as a solvent for the peroxycarboxylic acid. The selected saturated aliphatic tertiary alcohol should be free of non-complexed heavy metals and should dissolve enough of the peroxycarboxylic acid to make up the desired concentration of the acid. The saturated aliphatic tertiary alcohol can be employed alone, or as the major ingredient in a solvent mixture containing minor amounts of other inert organic solvents.

The tertiary alcohols which are suitable for stabilizing peroxycarboxylic acids must be free of oxidizable groups which can react with these acids. For this reason, oxidizable functional groups including unsaturated hydrocarbon and non-hydrocarbon groups cannot be present on the tertiary alcohol. The aliphatic chains of the tertiary alcohol can be branched or straight chained and can be of different lengths.

The length of the aliphatic chain does not affect the stabilizing eflect of the tertiary alcohol on peroxycarboxylic acids. However, as the number of carbon atoms in the chains increases, the molecular weight of the tertiary alcohol also increases. Further, as the molecular weight of the tertiary alcohol increases, the solubility of the peroxycarboxylic acid in the alcohol may, depending upon the specific peroxycarboxylic acid employed, decrease. Accordingly, the size of the alkyl groups in the tertiary alcohols which can be employed is limited only by the amount of peroxycarboxylic acid which is to be dissolved in the tertiary alcohol solvent.

The preferred members of the group of tertiary alcohols are tert-butyl alcohol and tert-amyl alcohol. These alcohols are relatively inexpensive and possess high solvent powers for most peroxycarboxylic acids.

Impurities in the tertiary alcohol may cause decomposition of the peroxycarboxylic acid solutions as in Equation I, or may be oxidized by the peroxycarboxylic acids, thus wastefully consuming them. The offending impurities generally are heavy metals, primary and secondary alcohols and olefins.

Heavy metals initiate catalytic decomposition of the peroxycarboxylic acid, and therefore, are highly undesirable, even in small amounts. Two methods can be employed to eliminate decomposition. The first of these is to remove the heavy alcohol in glass or glass-lined equipment. Another is to render the heavy metals inactive by adding a small amount, on the order of about ppm, of a metal chelating agent.

A compound such as dipicolinic acid is an ideal chelating agent, and effectively ties up the heavy metal in a complex organic structure, thereby making it unavailable for initiating decomposition of the peroxycarboxylic acid.

'While a metal chelating agent such as dipicolinic acid is metals by distilling the tertiary.

be obtained by the use of chelating agents with solvents other than tertiary alcohols.

The primary and secondary alcohols are undesirable impurities because they interact with the peroxycarboxylic acid to yield carboxylic acids and ketones respectively, thereby contributing to the decomposition of the peroxycarboxylic acid. Olefinic impurities are offensive because they react with the peroxycarboxylic acid to form epoxy and carboxy derivatives. Ketone, aldehyde, and amine impurities should also be avoided as these react with the peroxycarboxylic acid.

The present tertiary alcohols can be used alone or in admixture with minor amounts of organic solvents which do not have oxidizable substituents. Minor amounts or organic solvents such as benzene, and n-heptane have been found quite suitable. The amount of tertiary alcohol in the solvent mixture which is required to maintain the stabilizing action varies with the specific tertiary alcohol and the added solvent. However, it has been found that upwards of about 80% of the presently described tertiary alcohol is generally required to assure obtaining the full stabilizing effect.

The peroxycarboxylic acids which can be stabilized by the present class of organic solvents include aromatic peroxy-carboxylic acids, branched or straight chain saturated aliphatie peroxycarboxylic acids, and saturated cycloaliphatic peroxycarboxylio acids. These peroxycarboxylic acids can be substituted or unsubstituted, provided that the substituent groups are those which are not oxidized by peroxycarboxylic acids. Groups which are oxidizable, and therefore unsuitable, include primary and secondary alcohols, phenols, ketones, aldehydes and amines. Non-oxidizable groups, e.g., nitro, tertiary hydroxy, and fluoro substituents are acceptable.

Among the aromatic peroxycarboxylic acids which can be stabilized by the present solvents are peroxybenzoic acid, as well as the substituted aromatic peroxycarboxylic acids such as ortho-chloroperoxybenzoic acid, parachloroperoxybenzoic acid, para-nitroperoxybenzoic acid, and others containing similar non-oxidizable substituents.

Aliphatic peroxycarboxylic acids which can be stabilized by the present class of tertiary alcohols include straight chained compounds such as peroxyacetic acid, peroxybutyric acid, peroxypropionic acid, peroxylauric acid, as well as substituted aliphatic peroxycarboxylic acids such as monochloroperoxyacetic acid. Among the branched chained members of this group which can be employed are peroxy isobutyric acid, 2,2,4,4-tetramethyl peroxypentanoic acid, 3,5,5 -trimethylperoxyhexanoic acid, Z-methyl, 2,3-dichloroperoxypropionic acid, and trifiuoroperoxyacetic acid.

The cycloaliphatic peroxycarboxylic acids can be stabilized in the same manner as the acyclic members of this class. Among the acids which are suitable are peroxycyclohexanoic acid, peroxydecalincarboxylic acid and other substituted and nonsubstituted cycloaliphatic peroxycarboxylic acids.

The following examples illustrate the stabilizing efiect of the specified tertiary alcohols and are presented as representative of the present invention, but are not intended as limitative thereof.

EXAMPLE 1 Solid peroxybenzoic acid was dissolved in various organic solvents as shown in Table I. The solutions were analyzed for their active-oxygen content by titration with 0.1 N N21 S O solution in the presence of acetic acid. The solutions were placed in bottles in a dark place and stored at room temperature for a period of time. Then they were analyzed for the remaining peroxybenzoic acid content after storage. The stability of the solution was found by determining the losses of active oxygen during the storage period and calculating the amount of oxygen lost as percent loss. The results are presented in Table I.

The data show that peroxybenzoic acid dissolved in tert-butyl alcohol lost only 0.8% to 2.0% of its active oxygen after three weeks storage at room temperature, While solutions in other organic solvents lost 25 to 99%.

EXAMPLE 2 Peroxybenzoic acid solutions in various organic solvents were prepared the same way as described by Example 1. Dipicolinic acid was added to each solution. In tertbutyl alcohol only 50 p.p.m. could be added because of limited solubility. In other solvents 200 ppm. was added. The stability of these solutions was tested after the reported time intervals in the manner of Example 1. The results obtained are reported in Table II.

As seen in Table II, the peroxybenzoic acid in tert-butyl alcohol lost only 0.7% to 1.2% per month of its active oxygen, compared with solutions in other organic solvents where 17% to 99% were lost.

EXAMPLE 3 Peroxybenzoic acid was dissolved in a mixed solvent containing tert-butyl alcohol. To some of these solutions dipicolinic acid was added. The samples were stored at room temperature and the storage stability was determined the same way as described in Example 1. The results are shown in Table III.

The data show that peroxybenzoic acid solutions in mixed solvents containing tert-butanol and dipicolinic acid lost only 0.5% to 1.0% of its active oxygen after storage for one month at room temperature.

EXAMPLE 4 Solid peroxybenzoic acid was dissolved in tert-butyl a1- cohol and was stored at the various temperatures and concentrations given in Table IV, Additionally, other solvents were employed to make up solutions of peroxyenzoic acid. The solutions, additives, and active-oxygen losses are given in Table IV. The storage stability was determined using the same procedure as Example 1.

The results, reported in Table IV, show that peroxybenzoic acid solutions in tert-butanol did not lose any active oxygen when stored for two months at 14 C. or below. The same solution when stored at 25 C. lost only 1.57% of its active oxygen. When per-oxybenzoic acid was dissolved in chloroform, or chloroform-chlorobenzene mixture, the solutions lost 15% to 20% of their active oxygen after one months storage at +4 C. and 88% after three weeks at room temperature. This solvent, chloroform mixed with benzene, was advised by Kalthoff et al., J. Polymer Sci., 2, 199 (1947), as one of the best solvents for preparation of peroxybenzoic acid solutions.

EXAMPLE 5 A 25.0% by weight solution of peroxybenzoic acid in 3,6-dimethyl-3-octanol was made up which contained 50 ppm. of dipicolinic acid. The solution was stored at room temperature (24 to 25 C.) for 30 days. The amount of peroxybenzoic acid was determined at the end of the 30 days in the manner described in Example 1 and was found to have decreased to 24.74%.

EXAMPLE 6 A 15.0% by weight solution by weight solution of peroxybenzoic acid in 1,l-diethyl-l-propanol was made up which contained 50 ppm. of dipicolinic acid. The solution was stored at room temperature (24 to 25 C.) for 31 days. The amount of peroxybenzoic acid was determined at the end of the 31 days in the manner described in Example 1 and was found to have decreased to 14.81% by weight.

EXAMPLE 7 Two solutions of peroxybenzoic acid were made up; one contained 28.0% by weight peroxybenzoic acid dissolved in tert-amyl alcohol, the other contained 44.0% by weight peroxybenzoic acid dissolved in tert-butyl alcohol. Each of the solutions contained 50 ppm. of dipico- 5 limit: acid. The solutions were maintained at room temperature (24 to 25 C.) for 28 days. Thereafter, the solutions were tested in the manner described in Example 1 to determine the amount of peroxybenzoic acid remaining in the solutions; this was found to be 27.69% in the ofperoxylauric acid was determined at the end of the 30 EXAMPLE l1 tert-amyl alcohol solution, and 43.51% in the tert-butyl A 19.5% by weight solutlon of peroxybutyrlc acld 1n alcohol solution, tert-butyl alcohol was made up which contained 50 p.p.m. EXAMPLE 8 of dlpicolinic acid. The solution was maintained at room teme r t 2 Three solutions were made up by dlssolvlng orthoof 35? 3 23 23 532 g f z ff i chloroperoxybenzoic acid, para-chloroperoxybenzoic acid termineg in manner descriged g 1e S; and para-nitroperoxybenzoic acid in tertiary butyl alcohol. found to be 19 347 p w The concentrations of these solutions are reported in Table V. The samples were stored at room tempertaure for a EXAMPLE 1 2 period of 8 days. At the end of this tune, the amount of peroxycarboxylic acid was determined using the same by Welght sollltlon 0f P Y fy P procedure as Example 1. The results are shown in Table Field 111 y Was made p Which comallled 50 p.p.m. of dlplcollnlc acld. The solution was maintained EXAMPLE 9 at room temperature (24 to 25 C.) for 30 days. At the end of this period, the amount of peroxycyclohexg clght sohtlon of gaf 3 anoic acid was determined in the manner described in Extart u i i up 1 1c con l; d ample 1, and was found to be 12.16%.

P-P- I P21 1111c i 3? c f 3? g ,5; Pursuant to the requirements of the patent statutes, the at an e evfate f ureflo d F d i g principle of this invention has been explained and exemi g f i acl a .8 3 9 plified in a manner so that it can be readily practiced by 0 i. 6 g ig g m those skilled in the art, such exemplification including l 18 was Gun to e s owmg no 055 what is considered to represent the best embodiment of tlve oxygen. EXAMPLE 10 the invention. However, it should be clearly understood that, within the scope of the appended claims, the inven- An 18.3% by weight solution of peroxylauric acid in tion may be practiced by those skilled in the art, and hav- M t ab t l l h l w m d up a d maintained at room lng the benefit of this dlsclosure, otherwise than as spetemperature (24 to 25 C.) for 30 days. The amount clfically described and exemplified herein.

Table I Perbenzoic acid concentration after storage 2 Perbenzoie acid c0110. 1 2 Solvent Used before storage, wt. percent Stor. Cone, Percent Stor. Cone, Percent time, wt.perlosses time, wt. per-- losses days cent days cent Tert-butyl alcohol 5. 38 13 5. 34 0. 8 22 5. 34 0. 8

Do 25.5 14 24. 9 2. 34 28 25.0 1. 95 Benzene 9. 04 10 7. 55 16. 5 20 6. 52 27. 8 Diethyl et 13. 25 10 6. 82 48. 5 20 2. 95 77. 7 Benzene, 90% 9. 14 7.90 15. 8 23 7. 05 25. 0 Chloroform 6. 90 15 0. 95 86.3 31 0. 01 99. 9 Chlorobenzene. 33. 3 7 23. 7 28. 8 Dioctylphthalate 35. 5 10 32. 05 9. 7 28 26. 5 25. 3 n-Butyl alcohol- 8. 62 13 3. 09 63. 0 22 1. 46 83. 0 Sec-buty1 alcohoL. 7. 25 13 0. 82 88. 5 22 0. 07 99. 0 Iso-butyl alcohol- 9. 72 13 3. 88 60.0 22 2. 19 77. 5 Iso-propyl alcohol- 9. 33 13 1. 87 80. 0 22 0. 88 90. 5 Acetic acid 5. 58 13 3.15 43. 5 22 2. 32 58.3

1 By active oxygen determination. 2 Storage at 24 to 25C.

Table II Analyses results after storage 1 Gone. DPA2 before 1 2 3 Solvent Used added, storage,

p.p.m. wt.

percent Stor. 00110., Percent Stor. Cone, Percent time, wt. losses time, wt. losses days percent days percent 1 l 25.5 14 25.4 0.4 28 25.3 o. 78 lffilll'iflf.-- 50 40. 0 7 39. 7 0. 21 39. 5 1. 25

Do- 50 40. 2 14 40. 4 0 27 39. 7 1. 2 Benzene 0 04 g g -h t 10 200 9.40 l f r 200 6. 15 0. 86. 3 31 0. 01 99. 9

9 hl oben- 25i: lll n 200 5. 82 6 3. 64 36.3 22 0. 70 88.0 Dioctylphthalate. 200 35. 5 10 34. 1 4. 0 38 2. 95 17. 0 Chlorobenzene 200 33. 3 7 31. 5 5. 4

1 Storage was at 22 to 25 C. 2 Dipicolinic acid.

7' 8 Table III Analyses results after storage 1 Cone. DPA before 1 2 3 Solvent Used added, storage,

ppm. wt.

percent Stor. Cone, Percent Stor. Cone, Percent Stor. Cnc., Percent time, wt. losses time, w losses time, wt. losses days percent days percent days percent Tert-butanol, 85%; benzene,

n-hcptane, 5% 0 40. 7 7 40. 4 0. 74 14 39. 7 2. 46 28 39.1 3. 90 0 100 40. 7 7 40. 7 0 14 40. 5 0. 49 28 40. 4 0.74 Tert-butanol, 85%; benzene, 15 100 40. 2 27 40. 0 0. 5 Tcrt-butanol n-heptane, 15%-"; 100 40.4 27 40.0 1.0

1 Storage was at 24 to 25 O. 1 Dipicolinic acid.

Table IV Conc. Cone. DPA before Stor. Stor. wt. Percent Solvent Used added, storage, time temp, percent losses p.p.m. wt. perdays O. after cent storage Tort. =butyl alcohol 0 25. 5 58 4 25. 5 0 D0 25. 5 58 4 25. 5 0 0 25.5 58 14 25. 5 0 50 25. 5 58 14 25. 5 0 D0 5O 25. 5 58 25 25. 1 1. 57 Washed chloroform 0 6. 58 35 4 5. 31 19. 4 O 200 6. 58 35 4 5. 34 18. 8 Washed chloroform 90% chlorobenzene 10% 0 5. 82 22 4 4. 81 17. 3 D0 200 5. 82 22 4 4. 92 15. 3 DO 200 5. 82 22 25 0. 70 88. 0

Table V Analyses After Storage 1 DPA 2 Cone. be- Stor. Cone, Peroxy carboxylic acid Solvent added, fore stor., time, wt.

p.p.m. wt. days percent percent Ortho-ehloroperoxy bcnzoic Terltialrlylbutyl 100 39. 7 8 39. 4

a co 0 Para-chloroperoxy benzoic..- do 0 22. 9 8 22. 9 Para-nitroperoxy benzoie do 0 10.52 8 10. 35

1 Storage was at 24 to 25 C. 2 Dipicolinic acid.

What is claimed is:

1. A stable composition which consists essentially of a peroxy carboxylic acid, said acid being free of groups which can be oxidized by peroxy carboxylic acids, dissolved in an inert organic solvent containing a saturated aliphatic tertiary alcohol in amounts sufficient to prevent substantial decomposition of said peroxy carboxylic acid, said alcohol being free of oxidizable groups which will react with said acid.

2. The composition of claim 1 which contains dipicolinic acid in amounts up to 200 ppm.

3. The composition of claim 1 which contains said saturated aliphatic tertiary alcohol in amounts of at least 80% of a solvent mixture.

4. The composition of claim 1 alcohol is tert-butyl alcohol.

5. The composition of claim alcohol is tert-amyl alcohol.

6. A stable composition consisting essentially of peroxy benzoic acid dissolved in an alcohol selected from the group consisting of tert-butyl alcohol and tert-amyl alcohol said alcohol being present in amounts sufiicient to stabilize said peroxybenzoic acid against substantial decomposition.

7, The method of stabilizing solutions of peroxy carin which the tertiary 1 in which the tertiary boxylic acids dissolved in an inert organic solvent, said acids being free of groups which can be oxidized by peroxy carboxylic acids, which comprises adding a saturated aliphatic tertiary alcohol to said solutions of peroxy carboxylic acids in amounts suflicient to stabilize said acids against substantial decomposition, said alcohol being free of oxidizable groups which react with said acids.

8. The method of claim 7 in which the saturated aliphatic tertiary alcohol stabilizer is present in an inert organic solvent mixture in amounts of at least 9. The method of stabilizing organic solutions of peroxy benzoic acid against substantial decomposition of said acids which comprises adding in stabilizing amounts an alcohol selected from the group consisting of tertbutyl alcohol and tert-amyl alcohol as a stabilizer for said acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,754,914 Stoddard Apr. 15, 1930 2,169,368 Murray et al Aug. 15, 1939 2,395,638 Milas Feb. 26, 1946 2,609,391 Greenspan et a1. Sept. 2, 1952 

1. A STABLE COMPOSITION WHICH CONSISTS ESSENTIALLY OF A PEROXY CARBOXYLIC ACID, SAID ACID BEING FREE OF GROUPS WHICH CAN BE OXIDIZED BY PEROXY CARBOXYLIC ACIDS, DISSOLVED IN AN INERT ORGANIC SOLVENT CONTAINING A SATURATED ALIPHATIC TERTIARY ALCOHOL IN AMOUNTS SUFFICIENT TO PREVENT SUBSTANTIAL DECOMPOSITION OF SAID PEROXY CARBOXYLIC ACID, SAID ALCOHOL BEING FREE OF OXIDIZABLE GROUPS WHICH WILL REACT WITH SAID ACID. 